Telephone-exchange system



H. W. MAcDOUGALL.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED JUNE 4. 19H.

1,329,004, Patented Jan. 27,1920.

I k m 5 (ELY A I- gwllHl Harry. WMmfim/gafl 4 W M UNITED STATES PATENT OFFICE.

HARRY W. MAGDOUGALL, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Application filed June 4, 1917.

To all whom it may concern:

Be it known that I, HARRY IV. MAC- DOUGALL, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to automatic ringing systems adapted for use with operators cord or link circuits, the object of the invention being to provide an improved and simplified circuit arrangement which will permit satisfactory operation over a much wider range than has been possible heretofore.

In the automatic ringing circuits used heretofore more or less trouble has been experienced due to the exacting requirements placed upon the tripping relays, whose function is to disconnect the ringing apparatus from the line upon the called subscriber removing the receiver from the switchhook. These requirements have been necessarily rigid with the types of circuits used, since it has been necessary to insure operation over lines of various lengths, and at the same time to insure that the relays do not operate under normal line conditions.

In accordance with a feature of this invention, a circuit arrangement is provided wherein a single relay is operated to automatically connect a ringing generator to the called line (upon an operator completing the switching connection), and to automatically disconnect this generator from the line upon the subscriber removing his receiver from the hook. This relay is first energized by momentary flow of direct current, and its armature is then looked up by the flow of current through its winding from the ringing generator.

The invention may be more clearly understood by reference to the following description considered in connection with the accompanying drawing, in which the figure is a diagrammatic view of an operators link circuit embodying this invention connected to a subscribers line circuit, all the apparatus being shown in its normal or unactuated condition.

In the drawing there is shown a telephone exchange system embodying this invention Specification of Letters Patent.

Patented Jan. 27, 1920.

Serial No. 172,672.

and comprising subscribers lines A and B, terminating at a central oilice, and a cord circuit C thereat for interconnecting the subscribers lines. It will, of 'course, be understood that a plurality of subscribers lines similar to A and B terminate at the central ofiice, but for the sake of simplicity there is shown in the drawing only so much of a telephone exchange system as is necessary for a comprehension of the present invention.

Let it be assumed that subscriber A desires to be connected with subscriber B, in which case subscriber A signals the central ofiice in the. usual manner. The operator upon being advised that subscriber A desires to be connected to the line of subscriber B inserts the calling plug 1 of cord circuit C into the jack 2 of line B, whereupon relays 6 and 7 are operated and supervisory lamp 4: illuminated over a circuit from the grounded source of energy 8, through the supervisory lamp l, resistance 5, winding of ringing relay 6, sleeve contact of plug 1, sleeve of jack 2, and the winding of cutoff relay '7 to ground. The operation of relay 7 serves to disconnect the line relay 8 from the line in the well-known manner. Upon the energization of relay 6, armature 9 is attracted, and in its movement engages and passes under switch 10, causing momentary closing of the switch contacts, which provides a path for current flow from a grounded source of energy 12, through switch 10, and windings 13 and 14 of relay 11 to ground, thereby causing the attraction of armatures 15 and 16. In the operation of relay 11, armature 15 moves away from back contact 17, and engages front contacts 18 and 19, while simultaneously armature 16 is disconnected from back contact 20 and engages front contact 21. This operation results in connecting ringing current from the ringing generator 22 to line of subscriber B, through the resistance 26, the front contacts 19 and 21, and armatures 15 and 16 respectively of relay 11, and the tip and ring contacts of plug 1 and jack 2. Relay 11 is of the split-phase type, armatures 15 and 16 being joined together rigidly and the condenser 23 being connected in parallel with one of the windings 13 to insure satisfactory operation on alternating or pulsating current. This relay is maintained in an operated condition by means of current flowing from generator 22, through contact 19, armature 15, contact 18, winding 13 in parallel with condenser 23, and winding 1 1 to ground. The flow of ringing current to line of subscriber A is prevented by the opening of the circuit at the back contacts 17 and 20 of relay 11.

Subscriber B upon responding to the call removes the receiver from the switchhook, thereby placing the comparatively low resistance of the transmitter and induction coil winding in parallel with the windings of relay 11, causing the latter to be deenergized and the ringing circuit interrupted, .Armatures 15 and 16 are then permitted to engage contacts 17 and 20 re spectively, restoring the talking circuit between subscribers A and B, the supervisory lamp 1 being extinguished by the operation of the supervisory relay 2 1, which places the resistance 25 in parallel with the lamp. The armature 9 of relay 6 remalns attracted so long as the sleeve contact of plug 1 engages the sleeve of jack 2. Upon the connection being taken down, this relay is deenergized and the projection of armature 9' passes over switch 10 in such a way as not to close the contacts of the switch.

In the circuit described above, ringing of the called party starts automatically upon the operator inserting the calling plug in the jack. Under certain conditions such an arrangement is not desired, and it is then possible to replace the switch 10 and relay 9 with a manually operated key, the function of which is to momentarily connect the battery 12 through the windings of relay 11, the operation or the circuit otherwise being identical with that just described.

What is claimed is:

1. A telephone exchange system, comprising a telephone line, a link circuit for connecting thereto, a source of alternating signaling current, a split-phase relay for connecting said source of current to the line, means for operating said relay and additional means for maintaining said relay in an operated position.

2. A telephone exchange system comprising a telephone line, a link circuit for connecting thereto, a source of signaling current, a relay, means to energize said relay to connect said source of current to the line, said means comprising a second relay operable upon the connection of the link circuit with the telephone line to cause the momentary operation of said first relay, additional means for maintaining said first relay in an operated position, and means toshunt said first relay to disconnect said' source of current from the line. 7

3. A telephone exchange system comprising a telephone line, a link circuit for connecting thereto, a source of signaling current, a relay, means to energize said relay to connect said source of current to the line, additional means for directing said signaling current through the windings of said relay to maintain it energized, and a shunting circuit for said relay to disconnect said source of current from the line.

A. A telephone exchange system comprising a signal, a signaling circuit, a source of alternating signaling current, a relay adapted to operate on either direct or alternating current, means for initially operating said relay with direct current to connect said source of signaling current to said circuit, and additional means for directing said signaling current through the windings of said relay to maintain it energized.

5. A telephone exchange system comprising a signal, a signaling circuit, a source of alternating signaling current, a relay for connecting said source with said circuit, means for connecting a source of direct current to said relay to initially operate it, means for thereafter connecting said source of signaling current with said relay to maintain it operative, and means for shunting said source of signaling current to release said relay.

In witness whereof I hereunto subscribe my name this 31st day of May, A. D. 1917.

HARRY W. MACDOUGALL. 

